Two known digital logic systems are the ECL system and the TTL system. The TTL system operates using a single signal-carrying conductor and with potential levels of 0.8 volts and 2.0 volts (0.8 volts represents logical zero and 2.0 volts represents logical one). In the ECL system complementary signals are carried on two conductors, and potential levels of -1.8 volts on one conductor (the "principal conductor") and -0.65 volts on the other conductor (the "complementary conductor"), represent logical zero whereas logical one is represented by -0.65 volts on the principal conductor and -1.8 volts on the complementary conductor. The ECL system is superior to the TTL system for transmission of signals over long distances, because the ECL system has better noise immunity than the TTL system. On the other hand, many circuit components operating in the TTL system exhibit superior performance to equivalent components which operate in the ECL system. In addition, there are some functions that can be performed using circuit components which operate using TTL voltage levels but cannot be performed satisfactorily using components which operate using ECL voltage levels. For example, high speed (vistate drivers using TTL voltage levels are readily available, but drivers which operate using ECL voltage levels are not readily available.